What to do in the event of a nuclear attack2:18

What would you do if you were told a nuclear attack was 15 minutes away?
It's a frightening scenario but one which some experts claim Americans need to consider.

February 11th 2018

a month ago

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Mystery surrounds the source of a tiny particle of artificially enriched uranium found floating above Alaska. Was it North Korea? Picture: APSource:AFP

EVERYTHING was going according to routine.

The NOAA pollution-detecting flight was flying its well-worn track seven kilometres high in the skies between Alaska and Hawaii.

Their job was to sample the air. How much man-made material is in the ionosphere can, after all, have serious influences on public health and climate conditions.

But, one day in August 2016, their equipment registered an alarming blip.

It was a single particle, so small it could easily be suspended in the air.

What made this one so different was that it was radioactive.

It contained a minuscule fragment (just 580 nanometres) of uranium.

And that set off alarm bells.

Where did it come from?

Fukushima? China? North Korea?

A WB-57 high-altitude aircraft like the one used by NOAA to sample the atmosphere. One detected a radioactive particle in the skies between Alaska and Hawaii in 2016. Picture: NOAASource:Supplied

FORENSIC TRAIL

Uranium is common in nature. It exists underground, slowly going through a decay chain that takes it through a series of ever-less radioactive states until it eventually becomes inert rock, like granite.

Sometimes, through bushfires or dust storms, traces can get airborne.

But uranium can also be manipulated. Artificial processes can make it more radioactive — for use in nuclear reactors, and weapons.

The tiny aerosol particle was found to contain two types: uranium-238, and uranium-235.

There’s nothing surprising about uranium-238. It’s common in nature, if not in the atmosphere.

But uranium-235 is only very rarely natural. It’s almost always the product of refinement. It’s capable of initiating a fission chain reaction.

“During twenty years of aircraft sampling of millions of particles in the global atmosphere, we have rarely encountered a particle with a similarly high content of U-238 and never a particle with enriched U-235,” they write.

“The bulk of the particle probably came from combustion of heavy fuel oil,” they say, referring to the U-238.

But when it comes to the U-235: “We don’t know the source for this particle. It may indicate a novel source where enriched uranium was dispersed.”

All this begs the question, where did it come from?

Researcher Dan Murphy told Gizmodo: “One of the main motivations of this paper is to see if somebody who knows more about uranium than any of us would understand the source of the particle.”

Ryoo Yog-Gyu shows seismic waves in North Korea on a screen at the Korea Meteorological Administration center after North Korea's sixth nuclear test. Picture: GettySource:Getty Images

SEEKING A SOURCE

“Analysis of wind trajectories and particle dispersion model results show that the particle could have originated from a variety of areas across Asia,” the researchers write.

At this stage, all researchers can do is speculate.

Did it come from a nuclear accident, such as Chernobyl in Ukraine or Fukushima in Japan?

Not likely. These both happened long enough ago that such a particle would have long since fallen from the sky.

But the air pollution experts know the wind currents that enter the skies between Alaska and Hawaii.

They come from Central Asia, including China, Japan — and Korea.

Exactly where remains speculation.

But there are possibilities.

The particle’s composition suggests it came from recently refined reactor-grade uranium.

“My best guess is that the source is North Korea,” nuclear expert Arnie Gundersen told EnviroNews.

A North Korea nuclear tunnel collapsed last year killing around 200 people amid fears of a massive radioactive leak.. Picture: The SunSource:The Sun

“North Korea has a small reactor and does have gas centrifuges for slightly enriching uranium 235 … It is possible in either creating new fuel or in extracting plutonium from fuel that has already been in their reactor, some enriched uranium escaped and went airborne.”

Also among speculation are fears North Korea’s Punggye-ri nuclear weapons test facility is on the brink of collapse.

In September last year it was revealed a series of tests in recent years had vaporised huge chambers beneath Mount Mantap.

Its ability to sustain more is in doubt.

South Korea’s national weather agency told parliament in October that it believed there was a 60m by 100m hollow space at the base of the mountain.

“Is there a risk of radiation”, parliamentarians asked.

“Should it sink, there is a possibility,” the weather advisers replied.

In November, unconfirmed reports emerged of a tunnel collapse at the Punggye-ri facility, killing hundreds of workers.